Location of compoments.

I have never understood the issue of having the equipment rack between the speakers.  It is generally placed back of the speaker plane. Stereo imagine after-all is an illusion created by our brain, based on how the vibrations coming from the left and right speakers are hitting our ears.  There is no "center speaker".  Sound-stage is created by the mixing on the recording.  Unless your equipment rack is placed in the path of the music being sent out of your speakers, can it truly make much of a difference.  And I say "much" as sound waves do not move in a straight linear path, and there could be some reflection off the rack.  But being able to "hear the shape of the rack", and in most rooms, could we really hear the difference?  Moving your own rack would be the only true test, but I personally have not heard a noticeable improvement in my system when moving the rack to the side.  

Not worth it. Get better cables and components and keep it where it is rather than spend more money on a longer version of the cables you are using now. Also it’s best to go with longer balanced cables to amp and keep sp cables short. 

Mono tube amps next to speakers with short runs of speaker cable. XLR interconnects from output of line stage, which are long, equipment on sidewall. 

+1 @bigtwin You can have your equipment between the speakers, but should avoid placing reflective surfaces (eg., equipment racks with glass doors, TVs, etc.). Equipment should not be stacked up and should be distributed at lower heights say less than 4 ft. Sound stage imaging, depth, etc., are an audio illusion generated inside our brain based on sound largely coming from the speakers and to a lesser degree sound reflected from front wall, floor, roof, side walls, and yes from any reflective surfaces from equipment rack. By moving your equipment rack to the side will not completely eliminate the problem since any sound reflecting from that surface still contributes to the overall presentation. I used to have my TV in between the main speakers, but I always covered the TV with a black cloth to minimize reflections.

Agree with @ozzy62 - the details of what you're putting in the middle, and how (flush with baffles, or further back?) makes all the difference. I do gear to the side for one system, and in the middle (but pushed back) for another. Both do great, and I'm not stressing one way or the other. The logistics of each room dictated the positioning.